One way to confirm if an individual has an allergy is through a skin prick allergy test. Doctors perform them to determine what allergen is causing a reaction and how best to treat an allergic reaction. So, what can someone expect during this commonly used test?
The Basics of a Skin Prick Allergy Test
A skin prick allergy test is typically performed either on the inside of the arm or on the back. A doctor may test for only a few substances or as many as 40 at a time. For each potential allergen, the skin will be pricked, and a small amount of the substance will be inserted where the skin was pricked. The surface of the skin is barely penetrated, and the tests rarely cause any pain or bleeding. A typical reaction will be a reddish, raised bump that will itch.
This type of allergy testing is commonly performed to determine what is causing symptoms for patients with allergic rhinitis, allergic asthma, atopic dermatitis, food allergies, and insect allergies. Your allergist may test for common substances including:
- Tree pollens, weed pollens, dust mites, and molds
- Cat and dog dander
- Medications like penicillin
- Bee venom
Skin prick tests can be performed on most people, including infants older than six months. They are not recommended if someone has previously had a severe allergic reaction. In this case, an individual may be so sensitive to some substances that even a small amount could result in anaphylaxis, a life-threatening reaction that causes skin rash, nausea, vomiting, difficulty breathing, and shock.
Some medications, such as antihistamines, many antidepressants, and some heartburn medications can interfere with skin prick test results. A health care provider will decide if it is okay for a person to discontinue taking these for the test or not. Finally, certain skin conditions like dermatographism, severe eczema, or psoriasis may limit the amount of clear skin a person has available to get an accurate test result.
Skin Prick Test Accuracy
It’s rare to have a false negative from a skin prick test. If someone has a negative result from an allergen, this usually means they are not allergic to that substance. However, it is possible to have a false positive. This can happen for two reasons.
For food-related allergies, the tests look for an antibody known as IgE (immunoglobulin E). During digestion, our bodies break down food into tiny pieces, making any IgE proteins so small that the body doesn’t detect them. The food proteins introduced during a skin prick test are larger than the natural proteins and may indicate that someone’s sensitivity to a certain food is greater than it really is.
Another cause of a false positive is cross-reactivity. For instance, peanuts are legumes, but so are green beans. A skin prick test may show a reaction to green beans when someone actually has a peanut allergy. This means that the same person could eat a green bean with no effect, but would suffer from an allergic reaction when eating a peanut. This is because the two legumes share a protein that the test is detecting.
Because of this, your allergist may run additional tests, such as a blood test, to ensure the accuracy of the test results.
You should expect to receive the results of your skin prick allergy test by the end of your doctor’s visit. The results of these tests can help guide how your doctor will move forward in creating your treatment plan.
If you are seeking treatment for asthma or allergies, contact Columbia Allergy, with convenient locations in California, Oregon, Idaho, and Washington. We take a patient-focused approach that views every person as an individual with unique challenges and goals.
This is not medical advice. If you suspect you may have allergies, please consult a healthcare provider for an appropriate diagnosis.